Prior Art Statement
The following patents are representative of the most relevant prior art known to the applicant at the time of filing the application:
______________________________________ U.S. Pat. No. 2,233,176 February 25, 1941 R. L. Melton et al 2,469,398 May 10, 1949 E. Meyer 3,950,149 April 13, 1976 H. Fukuda 3,980,453 September 14,1976 H. Fukuda 4,150,514 April 24, 1979 T. E. Douglass Foreign Patents 494,407 July 14, 1963 Canada 2,028,861 March 12, 1980 United Kingdom ______________________________________
It has been shown in U.S. Pat. No. 4,150,514 to Douglass, Apr. 24, 1979, that microwave energy can be used to heat a resin and refractory grain mix to a temperature within a range of 90.degree. C. to 120.degree. C., then compact the heated mix in a heated mold or hot press to produce a density within a range of from 2 to 4 grams per cubic centimeter. The compacted mass is continuously heated in the mold until the designed density is accomplished and the resin is converted to a solid state. Either a thermo-plastic or thermo-setting resin may be used.
U.S. Pat. No. 2,233,176 to Melton et al., Feb. 25, 1941, and Canadian Pat. No. 494,407 to Rowe, July 14, 1953, illustrate the use of high frequency electro-static energy for heating and then curing the resin bond in molded shapes supported within such an electrical field.
U.S. Pat. No. 2,469,398 to Meyer, May 10, 1949, shows first conventionally heating an abrasive mix in a mold to preheat the mix and then applying pressure to the material in the mold to cure the resin. The heat source is not specified nor is the temperature range.
British Pat. No. 2,028,861 to Obersby, Mar. 12, 1980, discloses the use of microwave energy on a preformed abrasive product or wheel to cure a resin bond ingredient of the mix.
The U.S. Pat. Nos. 3,950,149 of Apr. 13, 1976 and 3,980,453 of Sept. 14, 1976, both issued to Fukuda, disclose a process for making an abrasive and resin bond mix that is formed into a brick shape that is then heated with a microwave source of electrical energy. The heated brick is rolled out into a flat shape and grinding wheel blanks are cut out of the flat sheet. The blanks are heated in a conventional electrically heated tunnel kiln to cure the resin.